Measurement

Q. The two-wattmeter method is used to measure power in a balanced 3-phase circuit, drawing lagging current. The power factor, if one of the wattmeter reads zero is

1. 0.5
2. 0.8
3. 1.0
4. 0.0

Q.

What is full form of alt in keyboard of computer?

Q.

What do you mean by electrical resonance?

Q. An energy meter, having meter constant of 1200 rev/kWh, makes 20 revolutions in 30 seconds for a constant load . The load in kW is

1. 2

Q. The solution for the unknown resistance for a wheatstone bridge is

$R_x=\frac{R_2{R}_3}{R_1}$

where,
$R_1=100\pm 0.5\%$ $\Omega$, $R_2=1000\pm 0.5\%\Omega and$ $R_3=842\pm 0.5\%\Omega$

The range of the unknown resistance $R_x$ is

1. $8293.7\Omega to8546.3\Omega$
2. $8546.3\Omega to8672.6\Omega$
3. $8167.4\Omega to8293.7\Omega$
4. $8167.4\Omega to8546.3\Omega$

Q. Two wattmeters, which are connected to measure the total power in a three-phase system supplying a balanced load, read 10.5 kW and -2.5 kW, respectively. The total power and the power factor respectively, are

1. 13.0 kW, 0.334
2. 13.0 kW, 0.684
3. 8.0 kW, 0.52
4. 8.0 kW, 0.334

Q.

What Is a sinusoidal oscillator?

Q. The meter constant of a 230 V, 10 A watt-hour meter is 1800 revolutions per kWh. The meter is tested at half load and rated voltage and unity power factor. The meter is found to make 80 revolutions in 138 seconds. The meter error at half load is ______ % fast.

1. 0.817

Q. Two wattmeter method is used for measurement of power in balanced three-phase load supplied from a balanced three-phase system. If one of the wattmeters reads half of the other (other positive), then the power factor of the load is

1. 0.532
2. 0.632
3. 0.707
4. 0.866

Q. A 3-phase balanced load which has a power factor of 0.707 is connected to a balanced supply. The power consumed by the load is 5 kW. The power is measured by the two-wattmeter method. The readings of the two wattmeters are

1. 3.94 kW and 1.06 kW
2. 2.50 kW and 2.50 kW
3. 5.00 kW and 0.00 kW
4. 2.96 kW and 2.04 kW

Q. The minimum number of wattmeter(s) required to measure 3-phase, 3-wire balanced or unbalanced power is

1. 1
2. 2
3. 3
4. 4

Q. A moving coil ammeter has a uniform scale with 50 divisions and gives a full scale reading of 10 A. The instrument can read up to (1/5)th of a scale division with a fair degree of certainity. The resolution of the instrument (in mA) is _____.

1. 0.4
2. 4
3. 0.04
4. 40

Q.

What are the four types of potentiometers?

Q.

How are imaginary numbers used in real life$?$

Q. In a Maxwell's bridge circuit shown below,



$If{R}_3=10\Omega ,C=0.5mF,R_1=320\Omega and{R}_2=20\Omega$ at balance then _____ is the Q-factor for the unknown impedance at a supply frequency of 50 Hz.

1. 1.57

Q. A (0-10) mA PMMC ammeter reads 4 mA in a circuit. Its bottom control spring snaps suddenly. The meter will now read nearly

1. 10 mA
2. 8 mA
3. 2 mA
4. zero

Q. A dynamometer type wattmeter responds to the

1. average value of active power
2. average value of reactive power
3. peak value of active power
4. peak value of reactive power

Q. A 0 - 10 A ammeter has a guaranted accuracy of 1.5% of full scale reading. The current measured by the instrument is 2.5 A. The percentage limiting error in the measurement is $\pm$ ________ %

1. 0.6
2. 6
3. 1.5
4. 3

Q. A moving coil instrument having a resistance of $10\Omega$, gives a full-scale deflection when the current is 10 mA. What should be the value of the series resistance, so that it can be used as a voltmeter for measuring potential difference up to 100 V?

1. $9990\Omega$
2. $990\Omega$
3. $9\Omega$
4. $99\Omega$

Q. A rectifier type AC voltmeter consists of a series resistance $R_s$ an ideal full-wave birdge rectifier and a PMMC instrument as shown in the figure. The internal resistance of the instrument is $100\Omega$ and a full scale deflection is produced by a DC current of 1 mA. The value of $R_s$. required to obtain full scale deflection with an AC voltage of 100 V(rms)applied of the input terminals is

1. $63.56\Omega$
2. $69.93\Omega$
3. $89.93\Omega$
4. $141.3\Omega$

Q. The inductance of a certain moving-iron ammeter is expressed as:
$L=10+3\theta -\left({\theta }^2/4\right)\mu H$, where $\theta$ is the deflection in radians from the zero position. The control spring torque in $25\times {10}^{-6}Nm/radian.$ The deflection of the pointer in radian when the meter carries a current of 5 A, is

1. 2.4
2. 2.0
3. 1.2
4. 1.0

Q. A digital voltmeter has $4\frac{1}{2}$ digit display is operated in selected voltage range of 2 V, the sensitivity of DVM is______mV.

1. 0.1

Q. In the Permanent Magnet Moving Coil (PMMC) instruments, damping is provided by

1. The coil spring attached to the moving coil
2. The aluminium frame to the moving coil
3. Damping vane in the air tight chamber
4. Eddy current disk

Q. The AC bridge shown in the figure is used to measure the impedance Z.

If the bridge is balanced for oscillator frequency f=2 kHz, then the impedance Z will be

1. $(260+j0)\Omega$
2. $(0+j200)\Omega$
3. $(260-j200)\Omega$
4. $(260+j200)\Omega$

Q. Which of the following quantity can be directly measured using CRO?

1. Voltage
2. Current
3. Phase difference
4. Frequency

Q. A $4\frac{1}{2}$ digital voltmeter is used for voltage measurement choose the correct statement(s) regarding $4\frac{1}{2}$ DVM.

1. The resolution of given DVM is 0.0001
2. Meter cannot distinguish between values that differ from each other by less than 0.001 of full scale.
3. 12.98 would be displayed on 10 V ranges, like 12.980 V
4. 0.81776 would be displayed on 1 V ranges, like 0.8177 volts

Q. A moving coil instrument whose resistance is $25\Omega$ given a full-scale deflection with a voltage of 25 mV. The instrument is to be used with a series multiplier to extend its range to 10 V. Then the error caused by ${10}^{\circ }C$ rise in temperature is (The temperature coefficient of copper is $0.004\Omega /{\Omega }^{\circ }C$ and that of margin $0.00015\Omega /{\Omega }^{\circ }C$)

1. 0.16% low
2. 0.16% fast
3. 0.24% low
4. 0.24% fast

Q. The power flow in a 3-phase, 3-wire balanced delta connected load is measured by the two wattmeter method. The reading of wattmeter 'A' is 6000 W and on wattmeter 'B' is -1000 W. If the voltage of the circuit is 440 V, 50 Hz. What is the value of capacitance connected in delta at the source to cause the whole of the power measured by wattmeter A only?

1. $272\mu F$
2. $251\mu F$
3. $224\mu F$
4. $312\mu F$

Q. A voltmeter having reading of 70 V on its 100 V range and an ammeter having reading of 80 mA on its 150 mA range are used to determine power dissipation in a resistor. Both these instruments are guaranteed to be accurate within $\pm 2\%$ at full scale deflection. The limiting error (in percentage) in power measuement is _______

1. 6.6
2. 0.66
3. 2.857
4. 3.75

Q. The pressure coil of a dynamometer type wattmeter is

1. highly inductive
2. highly resistive
3. purely resistive
4. purley inductive